InFOCuS hard x-ray telescope: pixellated CZT detector/shield performance and flight results (original) (raw)
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Design and testing of a prototype pixellated CZT detector and shield for hard- x-ray astronomy
EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy X, 1999
We report on the design and laboratory testing of a prototype imaging CZT detector intended for balloon flight testing in April 2000. The detector tests several key techniques needed for the construction of large-area CZT arrays, as required for proposed hard X-ray astronomy missions. Two 10 mm × 10 mm × 5 mm CZT detectors, each with a 4 × 4 array of 1.9 mm pixels on a 2.5 mm pitch, will be mounted in a "flip-chip" fashion on a printed circuit board carrier card; the detectors will be placed 0.3 mm apart in a tiled configuration such that the pixel pitch is preserved across both crystals. One detector is eV Products high-pressure Bridgman CZT, and the other is IMARAD horizontal Bridgman material. Both detectors are read out by a 32-channel VA-TA ASIC controlled by a PC/104 single-board computer. A passive shield/collimator surrounded by plastic scintillator surrounds the detectors on five sides and provides a ∼ 45 • field of view. The background spectrum recorded by this instrument will be compared to that measured by a single-element CZT detector (10 mm × 10 mm × 2 mm high-pressure Bridgman material from eV Products) fitted with the same passive/plastic collimator but including an active BGO shield to the rear. This detector has been previously flown by us completely shielded by a passive cover. We describe preliminary laboratory results for the various systems, discuss initial background simulations, and describe our plans for balloon flight tests.
X-Ray and Gamma-Ray Instrumentation for Astronomy XI, 2000
We report on the construction and laboratory testing of pixellated CZT detectors mounted in a flip-chip, tiled fashion and read out by an ASIC, as required for proposed hard X-ray astronomy missions. Two 10 mm × 10 mm × 5 mm detectors were fabricated, one out of standard eV Products high-pressure Bridgman CZT and one out of IMARAD horizontal Bridgman CZT. Each was fashioned with a 4 × 4 array of gold pixels on a 2.5 mm pitch with a surrounding guard ring. The detectors were mounted side by side on a carrier card, such that the pixel pitch was preserved, and read out by a 32-channel VA-TA ASIC from IDE AS Corp. controlled by a PC/104 single-board computer. A passive shield/collimator surrounded by plastic scintillator encloses the detectors on five sides and provides a ∼ 40 • field of view. Thus this experiment tests key techniques required for future hard X-ray survey instruments. The experiment was taken to Ft Sumner, NM in May 2000 in preparation for a scientific balloon flight aboard the joint Harvard-MSFC EXITE2/HERO payload. Although we did not receive a flight opportunity, and are currently scheduled to fly in September 2000, we present our calibration data in the flight configuration together with data analysis techniques and simulations of the expected flight background spectrum.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
We successfully carried out the first high-altitude balloon flight of a wide-field hard X-ray coded-aperture telescope ProtoEXIST1, which was launched from the Columbia Scientific Balloon Facility at Ft. Sumner, New Mexico on October 9, 2009. ProtoEXIST1 is the first implementation of an advanced CdZnTe (CZT) imaging detector in our ongoing program to establish the technology required for next generation wide-field hard X-ray telescopes such as the High Energy Telescope (HET) in the Energetic X-ray Imaging Survey Telescope (EXIST). The CZT detector plane in ProtoEXIST1 consists of an 8 × 8 array of closely tiled 2 cm × 2 cm × 0.5 cm thick pixellated CZT crystals, each with 8 × 8 pixels, mounted on a set of readout electronics boards and covering a 256 cm 2 active area with 2.5 mm pixels. A tungsten mask, mounted at 90 cm above the detector provides shadowgrams of X-ray sources in the 30-600 keV band for imaging, allowing a fully coded field of view of 9 • × 9 • (and 19 • × 19 • for 50% coding fraction) with an angular resolution of 20. In order to reduce the background radiation, the detector is surrounded by semi-graded (Pb/Sn/Cu) passive shields on the four sides all the way to the mask. On the back side, a 26 cm × 26 cm × 2 cm CsI(Na) active shield provides signals to tag charged particle induced events as well as 100 keV background photons from below. The flight duration was only about 7.5 hours due to strong winds (60 knots) at float altitude (38-39 km). Throughout the flight, the CZT detector performed excellently. The telescope observed Cyg X-1, a bright black hole binary system, for ∼ 1 hour at the end of the flight. Despite a few problems with the pointing and aspect systems that caused the telescope to track about 6.4 deg off the target, the analysis of the Cyg X-1 data revealed an X-ray source at 7.2σ in the 30-100 keV energy band at the expected location from the optical images taken by the onboard daytime star camera. The success of this first flight is very encouraging for the future development of the advanced CZT imaging detectors (ProtoEXIST2, with 0.6 mm pixels), which will take advantage of the modularization architecture employed in ProtoEXIST1.
Pixel detectors for x-ray imaging spectroscopy in space
Journal of Instrumentation, 2009
Pixelated semiconductor detectors for X-ray imaging spectroscopy are foreseen as key components of the payload of various future space missions exploring the x-ray sky. Located on the platform of the new Spectrum-Roentgen-Gamma satellite, the eROSITA (extended Roentgen Survey with an Imaging Telescope Array) instrument will perform an imaging all-sky survey up to an X-ray energy of 10 keV with unprecedented spectral and angular resolution. The instrument will consist of seven parallel oriented mirror modules each having its own pnCCD camera in the focus. The satellite born X-ray observatory SIMBOL-X will be the first mission to use formation-flying techniques to implement an X-ray telescope with an unprecedented focal length of around 20 m. The detector instrumentation consists of separate high-and low energy detectors, a monolithic 128 × 128 DEPFET macropixel array and a pixellated CdZTe detector respectively, making energy JINST 4 P03012 band between 0.5 to 80 keV accessible. A similar concept is proposed for the next generation Xray observatory IXO. Finally, the MIXS (Mercury Imaging X-ray Spectrometer) instrument on the European Mercury exploration mission BepiColombo will use DEPFET macropixel arrays together with a small X-ray telescope to perform a spatially resolved planetary XRF analysis of Mercury's crust. Here, the mission concepts and their scientific targets are briefly discussed, and the resulting requirements on the detector devices together with the implementation strategies are shown.
CZT in Space Based Hard-X-ray Astronomy
2006
One of the key aspects of a detector material for space-borne hard X-ray and gamma-ray telescopes is the rate of prompt and delayed background events generated inside the material by charged and neutral particles striking the detector. These particles are Cosmic Rays, particles trapped in Earth's magnetic field, and secondaries from Cosmic Ray interacting with the atmosphere and the spacecraft. Here, we present a preliminary study of Cadmium Zinc Telluride (CZT) and its behaviour in space environments. We have used the simulation package MGGPOD to estimate the background of the CZT detectors in the proposed Energetic X-ray Imaging Survey Telescope (EXIST) for possible orbital parameters. The EXIST mission will make use of 6 square meters of 0.5 cm thick CZT detectors to record cosmic X-rays in the energy range from 10 keV to 600 keV. The detectors will be shielded by a fully or partly active shield. For the specific detector and shielding geometry considered here and an orbit with a low (7 deg) inclination, the background rate is dominated by the diffuse extragalactic below 200 keV. Prompt and delayed hadronic backgrounds grow increasingly important above this energy, becoming the main contributors to the total background above 1 MeV. A fully active shield performs slightly better than a half active/half passive shield.
Building large area CZT imaging detectors for a wide-field hard X-ray telescope—ProtoEXIST1
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009
We have constructed a moderately large area (32 cm 2), fine pixel (2.5 mm pixel, 5 mm thick) CZT imaging detector which constitutes the first section of a detector module (256 cm 2) developed for a balloon-borne wide-field hard X-ray telescope, ProtoEXIST1. ProtoEXIST1 is a prototype for the High Energy Telescope (HET) in the Energetic X-ray imaging Survey Telescope (EXIST), a next generation space-borne multi-wavelength telescope. We have constructed a large (nearly gapless) detector plane through a modularization scheme by tiling of a large number of 2 cm × 2 cm CZT crystals. Our innovative packaging method is ideal for many applications such as coded-aperture imaging, where a large, continuous detector plane is desirable for the optimal performance. Currently we have been able to achieve an energy resolution of 3.2 keV (FWHM) at 59.6 keV on average, which is exceptional considering the moderate pixel size and the number of detectors in simultaneous operation. We expect to complete two modules (512 cm 2) within the next few months as more CZT becomes available. We plan to test the performance of these detectors in a near space environment in a series of high altitude balloon flights, the first of which is scheduled for Fall 2009. These detector modules are the first in a series of progressively more sophisticated detector units and packaging schemes planned for ProtoEXIST2 & 3, which will demonstrate the technology required for the advanced CZT imaging detectors (0.6 mm pixel, 4.5 m 2 area) required in EXIST/HET.
Characterization of a CZT focal plane small prototype for hard X-ray telescope
IEEE Transactions on Nuclear Science, 2005
The promise of good energy and spatial resolution coupled with high efficiency and room temperature operation has fuelled a large international effort to develop cadmium zinc telluride (CZT) for hard X-ray applications. We are involved on the development of a hard X-ray telescope based on multilayer optics and focal plane detector operative in the 10-80 keV energy range. This telescope requires a high efficiency focal plane providing both fine spatial resolution and spectroscopy with a compact and robust design. This paper reports preliminary results on the characterization both in spectroscopic and spatial response of two small pixellated CZT detectors (10 10 1 mm 3 and 10 10 2 mm 3 single crystals) with 0.45 mm pixel size. We present the results obtained using both standard commercial read-out electronics Readout Electronics for Nuclear Applications (RENA) and innovative low noise and low power dissipation ASICs developed within the collaboration.
The hard X-ray response of the XIS-CCD for Astro-E: qualification of the X-ray CCD detector
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1999
We report on the hard X-ray response of the CCD detector for the X-ray imaging spectrometer (XIS), to be launched on the next Japanese X-ray Astronomical Satellite, ASTRO-E, in February 2000. XIS is prepared by an international team, comprised of MIT (USA), ISAS, Osaka University and Kyoto University (JAPAN). We have evaluated the X-ray response of the XIS in its high-energy band (1.5}10 keV). Data from the #uorescent line emission of Al, Cl, Ti, Ni, Fe, Zn, Se were used to construct the response function of the CCD detectors. Details of the response function } including the energy-scale, linearity, energy resolution, quantum e$ciency }, are given as a function of incident X-ray energy. We "nd that the tail component of high-energy photopeaks are produced by events with incomplete charge collection. We also conclude that the size of the charge clouds can be estimated using the shapes of the tail components.
Characterization of Redlen CZT detectors for hard x-ray astronomy
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XX
We present the results of ongoing characterization of Cadmium Zinc Telluride (CZT) semiconductors produced by Redlen Technologies. In particular we hope to determine their viability for future X-ray astronomy missions such as the High Energy X-ray Probe (HEX-P). The fully fabricated hybrid detectors consist of CZT crystals with a collecting area of 2 cm × 2 cm and thickness of 3 mm mounted on a custom pixelated ASIC originally designed for the Nuclear Spectroscopic Telescope Array (NuSTAR) mission, which launched in 2012. We present the results of inter-pixel conductance and leakage current tests as well as spectral characterization using an 241 Am source. Although further calibration and testing is necessary to determine the capabilities of these detectors, preliminary results indicate that Redlen CZT will be able to achieve spectral resolution and noise levels comparable to those of the CZT detectors currently in use aboard NuSTAR.
IEEE Transactions on Nuclear Science, 2000
New, high spatial resolution CdZnTe (CZT) and silicon (Si) pixel detectors are developed for high angular and high energy resolution x-ray astronomy. These detectors are proposed for use in wide field-of-view, imaging All-sky X-ray, and Gammaray Astronomy Monitor (AXGAM) in a possible future space mission. The high stopping power of CZT detectors combined with low-noise front-end readout electronics ASIC (Application Specific Integrated Circuit) makes possible an order of magnitude improvement in spatial (angular) and energy resolution in x-ray detection. The AXGAM instrument will be built in the form of a fine coded mask placed over two-dimensional, high spatial resolution and low energy threshold silicon and CZT pixel detector arrays. The preliminary test results obtained from our first silicon and CZT pixel detectors are presented. These detectors may also be used with or without modification for medical and industrial imaging.